Light Weight Directory Access Protocol (LDAP) has become very popular due to its efficient and fast data access. A large number of applications/services are currently being developed which use an LDAP directory as their centralized data repository.
The LDAP directory stores entries as a tree. Each entry may consist of one or more attribute names and attribute values. An entry may be uniquely identified by its distinguished name (DN) that may include a common name (cn) attribute of the entry and DN of a parent entry.
The contents of the entries are governed by an LDAP directory schema. The schema defines object classes, and each entry has an objectClass attribute containing named classes defined in the schema. The objectClass attribute may be multivalued, and contain the class “top” as well as some number of other classes. The schema definition for each class an entry belongs to defines what kind of object the entry may represent (e.g., a person, organization or domain). Membership in a particular class gives the entry the option of containing one set of attributes (optional attributes), and the obligation of containing another set of attributes (mandatory or required attributes). For example, an entry representing a person might belong to the class “person”. Membership in the “person” class would require the entry to contain the “sn” and “cn” attributes, and allow the entry also to contain “userPassword”, “telephoneNumber”, and other attributes.
Entries may be part of a group, for example, a static group. The static group is one which where membership is specified by presence in a list. Thus, a static group may comprises a list of members. The specific members are listed and identified by their attribute. Membership may change at any time, just as one might cross a name off the paper list or write in a new name. Such a potentially large static group may be either prone to error or not always up to date.